Radiation-induced disorder in compressed lanthanide zirconates

• Published in: Physical chemistry chemical physics : PCCP Vol. 20; no. 9; pp. 6187 - 6197
• Main Authors: Park, Sulgiye, Tracy, Cameron L, Zhang, Fuxiang, Park, Changyong, Trautmann, Christina, Tkachev, Sergey N, Lang, Maik, Mao, Wendy L, Ewing, Rodney C
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 2018
• Subjects: Amorphization; Defects; Fluorite; Frenkel defects; Ion irradiation; Radiation effects; Samarium compounds; Transformations; Zirconates
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c7cp08664d

The effects of swift heavy ion irradiation-induced disordering on the behavior of lanthanide zirconate compounds (Ln Zr O where Ln = Sm, Er, or Nd) at high pressures are investigated. After irradiation with 2.2 GeV Au ions, the initial ordered pyrochlore structure (Fd3[combining macron]m) transformed to a defect-fluorite structure (Fm3[combining macron]m) in Sm Zr O and Nd Zr O . For irradiated Er Zr O , which has a defect-fluorite structure, ion irradiation induces local disordering by introducing Frenkel defects despite retention of the initial structure. When subjected to high pressures (>29 GPa) in the absence of irradiation, all of these compounds transform to a cotunnite-like (Pnma) phase, followed by sluggish amorphization with further compression. However, if these compounds are irradiated prior to compression, the high pressure cotunnite-like phase is not formed. Rather, they transform directly from their post-irradiation defect-fluorite structure to an amorphous structure upon compression (>25 GPa). Defects and disordering induced by swift heavy ion irradiation alter the transformation pathways by raising the energetic barriers for the transformation to the high pressure cotunnite-like phase, rendering it inaccessible. As a result, the high pressure stability field of the amorphous phase is expanded to lower pressures when irradiation is coupled with compression. The responses of materials in the lanthanide zirconate system to irradiation and compression, both individually and in tandem, are strongly influenced by the specific lanthanide composition, which governs the defect energetics at extreme conditions.